Fuel injection control for freepiston units



May M, 1948. R. J. HOOKER FUEL INJECTION CONTROL FOR FREE PISTON UNITS Filed Jan. 16, 1,945 4 Sheets-Sheet 1 May 11, 1948. R. J. HOOKER FUEL INJECTION CONTROL FOR FREE PIST ON UNITS 4 Sheets-Sheet 2 Filed Jan. 16, 1945 NdE y 11, 1948- R. J. HOOKER T 2,441,195

rum. INJECTION common FOR FREE rts'rou uuns- Fild Jan. 16, 1945 {Sheets-Sheet} Has INVENTOR May 11, .1948. R. J. HOOKER 2,441,195

FUEL INJECTION CONTROL FOR FREE PISTON UNITS Filed Jan. 16, 1945 Y 4 Sheets-She et 4- l04 7 H6 I20 I02 H8 Y 88 yMASTER CONTROL 84 6 72 CONTROL FLU ID T0 INJECTION PUMP I56 I60 'ns FROM FUEL SUPPLY FIG.4.

INVENTOR FUEL HNJEUTION CONTROL FOR FREE- MSTON 3 Ralph ll. Hooker,

Manchester, Gonnl, assignor to United Aircraft Corporation,

East Hartford,

@onra, a corporation oi Delaware Application .ianuary 16, 19%, Serial No. 573,02"!

This invention relates to free-piston units and particularly to an injection device which will cause the unit to run more stably. 1

In these units the injection device is frequently actuated by piston reciprocation as by means of a cam mounted on the restraining linkage that connects the opposed pistons. If the length of the piston stroke changes the length of stroke of the pump plunger actuated by the cam is also changed. When the pump is filled through an inlet port that is covered by the plunger during a part of the stroke the filling time increases as the stroke lengthens and th filling time shortens as the stroke becomes shorter. This results in an unstable operating unit since as the plunger stroke shortens, less fuel is delivered to the engine cylinder, thereby delivering less energy to the pistons with the result that the stroke continues to shorten until the unit stalls. A feature of this invention is an injection device in which filling may occur for the entire length of the plunger stroke.

Another feature is the combination of a device of this type with a free-piston unit to cause more stable operation of the unit.

A feature of the invention is an injection pump, the filling port of which is uncovered during the entire plunger stroke so that the pump mayfill as soon as the plunger begins its filling stroke. Another feature is the combination with an injection pump of this character a throttling device by which the quantity of fuel supplied to the pump may be controlled.

A feature of the invention is the use of an injection pump of this character in conjunction with an overstroke control which permits the overstroke unit to operate directly'upon the duel supply for controlling the quantity of fuel delivered to the pump. In accordance with this feature, if the plunger is moved slowly within the casing, fuel will begin to. flow through the vent port with the plunger in the position at which the injection part of the cycle takes place.

Another feature of the invention is an arrangement for circulating fuel through the pump cylinder for each stroke of the plunger to assist in cooling the pump.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 1 is a sectional view through the. unit.

Fig. 2 is a sectional view of the restrainin linkage.

3 Claims. (in. IZMG) Fig. 3 is a sectional view through the injection device.

Fig. 4: shows an-overstoke control in conjunction with the arrangement for throttling the fuel supply.v

The unit shown includes an engine cylinder it having reciprocating pistons l2 and I l to which compressor pistons It and IS in cylinders 20 and 22 are integrally connected. Sleeves 2t and 26 attached to the compressor pistons complete the reciprocating piston assemblies. The sleeves in combination with stationary pistons 29 and 86 form air spring cylinders.

The piston assemblies are moved apart bythe burning of fuel injected into engine cylinder it through one or more nozzles 32. Air compressed in the air sprin cylinders on the power stroke returns the piston assemblies. The assemblies are always maintained at equal distances from the center of the engine cylinder by a linkage, which may include racks 3t and 38, Fig. 2, extending from the piston assemblies and meshing with a pinion 38 on a shaft til.

Intake manifold M, which extends around the compressor. and engine cylinders, conducts air to intake valves it in the heads of the compressor cylinders through which air alternately enters opposite ends of these cylinders. The compressed air leaves the cylinders through discharge valves 46, also at opposite ends of the compressor cylinders and passes into a central scavenge chamber t8 and end chambers 50 and 52. These chambers may be connected by a scavenge manifold, not shown.

Compressed gas from the chambers enters engine ports 54 and 58 which are uncovered by pistons [12 and it at the end of the power stroke, thereby permitting air to be blown through the engine cylinder. Gas in the engine cylinders is discharged through exhaust ports 58 into exhaust manifold Gil,

The'location of the outer end of the piston stroke is indicated by a master control 62. This control is actuated by a cam 64 turnin with the pinion 38, as shown in Fig. 2. Since this pinion is oscillated directly from the pistons, the movement of cam St is proportional to the piston stroke.

Fluid under pressure from a constant pressure source enters a passage I0 in a casing 12 through a conduit It. This passage intersects a bore 16 adjacent its outer end and a throttling screw it controls the rate of flow into bore 16. A branch passage from passage 10 connects with a port G2 in bore 16. A plunger 84 in 3 bore 18 has a groove 88 which connects a port 88 alternately with port 82 or a port 88. Port 88 is connected by a passage 82 to the inner vend of bore 18. Port 88 is connected by a channel 84 in casing 12 and in an adjacent casing 88 to the inner end of a bore 88 in casing 88.

A piston I88 in bore 88 is moved to the right by a calibrated spring I82. A plunger I84 extends through the piston and carries on its projecting end a push rod I88. This rod has a roller II8 held against cam 84 by a spring II 2. Plunger I84 has a central passage II4 connected with spaced grooves H8 and I I8 in the plunger. Groove H8 aligns with openings I28 in a sleeve I22 carried by piston I88 and groove H8 is adapted to be uncovered by the end of sleeve I22 as the plunger is moved to the right by the cam as the pistons approach the outer ends of their stroke.

Fluid under pressure from the right hand end of bore 18 enters the outer end of bore 88 through a connecting channel I24, moving piston I88 against the action of spring I82. As plunger I84 is moved by cam 84 the groove H8 is uncovered by sleeve I2h to permit discharge of fluid from the right hand end of bore 88 through plunger I84 and into the inner end of bore 98 which is vented, as will appear, The pressure in the right hand end of bore 88 varies in accordance with the compression of the spring, and as the piston stroke becomes shorter, the piston I88 moves inward increasing the spring tension and increasing the pressure at the end 0! bore 88.

Since the change in pressure on the outer end of plunger 84 is proportional to the change in the location of the end position of the piston stroke, the pressure on the inner end of plunger 84, which balances the pressure on the outer end, must vary in the same manner. In this way the pressure in the discharge conduit I28 is proportional to the spacing of the actual end of the piston stroke from the extreme outer position of the piston. and changes in the pressure of the fluid in this conduit will be proportional to changes in the end position of the piston stroke. This pressure (and change in pressure) may indicate on a calibrated gauge (not shown) the exact position of the end of the piston stroke and may be used for actuating the fuel control means.

The outer end of plunger I84 may reciprocate in a chamber I88 connectedb a conduit I82 to a sump. not shown. The inner end of bore 88 may be connected by a conduit I84 to conduit I 82. It may be advantageous to reduce pressure surges in channel I24 by means of a bellows I88.

Control fluid from the outer master control may be used to cut oil the supply or fuel in the event that the length of stroke becomes excessive or if the end of the actual piston stroke approaches outer dead center. As shown conduit I28 is connected to a port I42 in a casing I44 for the overstroke control. This port communicates with the end of a bore I48 in which a plunger I48 is slidable, this plunger being held in the position shown by a spring I 88,

Plunger I48 has a projecting stem I82 on the end of which is a tapered plug I84 engaging a seat I88 between the fuel inlet port I88 and-the fuel outlet port I88 which-is connected to the injection system.

The injection system, as shown in Fig. 3, has a casing I82 having a bore I 84 in which a plunger I88 reciprocates. The bore has an inlet port I88 located beyond the end of the plunger so that it is open during the entire plunger stroke to the space I18 at the head or the plunger. A check valve I12 prevents escape of fluid from port I88 and allows fuel to enter the space I18 through an inlet passage I14 connected by a conduit I18 to the outlet port I68 01 the over-stroke valve. A discharge port I18 in the bore I84 is adapted to be covered by the plunger during the pumping stroke. After port I18 is covered fuel is pumped through grooves I88 and passages I82 in a cufl I 84 to a chamber I88 located in a nozzle I88. A needle I88 is guided by a bore I92 in the nozzle body and is adapted to close a discharge port I84 for the chamber. The needle has a groove I88 by which fuel ma flow past the needle to the discharge port. A nozzle tip I98 controls the pattern of the fuel discharge into the engine cylinder.

A spring 288 normally holds the cull? in such a position that a flange 282 on the cuff prevents flow of fuel out of the chamber and into space I18. This spring also normally holds the needle I88 in a position to close the port I84.

As the plunger moves upwardly on the pumping stroke the pressure of the fuel in space I18 moves the cuil I 84 upward to permit fuel to enter the accumulator chamber I86. Fuel accumulates in the chamber until a spill port 284 in the casing communicates with an annular groove 288 in the plunger, thereby venting the space I18 through a passage 288 in the plunger. When this occurs. the drop in pressure in space I18 permits the pressure within the chamber to force needle I88 down so that fuel may discharge through groove I88 and passage l 84 into the engine cylinder.

At the completion of the pumping stroke of the plunger the plunger moves'down for the filling stroke and fuel enters the space I18 past check valve I12. While the plunger is in the position shown and during the first part of the downward movement of the plunger until the groove 288 no longer communicates with port 284 fuel under pressure may flow through passage 288 and discharge through the port 284 and a communicating passage 218. With the injection device installed in the free-piston unit the point at which injection takes place may be accurately checked by slowly moving the plunger I 88 down until fuel stops discharging from the open end of passage 2I8. This indicates the position of the plunger at the time the pump begins the injection part of its cycle so that the exact timing with respect to the pistons of the unit may be checked. The timing may be checked on the pumping stroke in a similar way.

It will be understood that the injection plunger may be reciprocated from a cam 2| 2 which, as shown in Fig. 2, is arrange to turn with the pinion 88 of the restraining linkage.

The fuel quantity may be adjusted by a throttle in the supply conduit I 18. This may be done either by a manually operated valve 2I4 or by means of the overstroke control of Fig. 4 which, as will be apparent, throttles the flow of fuel and thereby controls the quantity of fuel entering the space I18. By the use of the overstroke control above described, in conjunction with the injection system in which the filling port has a check valve and is always open to the pump bore, a very stable operation 01 the unit may be obtained.

It is to be understood that the invention is not limited to the specific embodiment herein illus-' trated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. In a fuel injection system for free-piston I units, each unit including opposed reciprocating pistons having variable strokes, a linkage connecting said pistons, and actuating means on said linkage for the fuel injection system, said system including a pump having a casing with a bore, a'plunger reciprocating in the bore and having a variable stroke, a filling port connecting with said bore at a point beyond the end ofthe plunger at the extreme end of its stroke, a connection to said port, a check valve in said connection, and

' said bore at a point beyond the end of the plunger at the extreme end of its stroke, a connection to said port, a check valve in said connection, a throttle valve for controlling the flow of fuel to said port, and means responsive to a change in the end position of the piston stroke for adjusting the throttle valve.

3. A device of the class described, a free-piston unit including engine and compressor cylinders, piston assemblies in said cylinders, and a linkage connecting said assemblies, in combination with an injection device for the unit actuated in response to reciprocation of said pistons, said device including a plunger connected to and actuated by said linkage, a casing having a bore in which the plunger reciprocates, and a filling port communicating with said bore at a point beyond the extreme end of the stroke of the-p1unger so that the bore may fill during the entire plunger stroke, a discharge port adapted to be uncovered by the plunger during its reciprocation, 'a check valve for controlling the flow of fuel from said inlet port, and a throttle valve for adjusting the flow to said inlet port.

RALPH J. HOOKER.

REFERENCES orran The following references are of record in the file of this patent: 

